[rcdmd]

Reading some comments in this thread you might think physicians are unable to apply Bayesian statistics to medical care. As a physician myself, I'd encourage a more considered line of thinking.

Clearly, physicians here failed to calculate an exact positive predictive value in the example. The question is does that inability affect their 1) medical care delivered and 2) communication with the patient and the patient's own informed decision-making.

In speaking to 1-- there are many examples to choose from from probably any medical specialty but let's stick to breast cancer screening since that's the example from the article. USPSTF presents their recommendations[1]. I'd encourage anyone with interest to at least skim the rationale presented on the page below those recommendations. They very well consider prevalence as well as efficacy of specific tests given the presence of different risk factors in a patient (age, family history, etc). Importantly, those and many other screening guidelines are applied by primary care physicians who may not otherwise be able to calculate exacting probabilities.

[1] https://www.uspreventiveservicestaskforce.org/Page/Document/...

In speaking to 2-- patient autonomy of course requires an appropriate understanding of the tests they receive, any risk to those tests and the benefits and harms of true positives, false negatives, etc. The associated frequencies, albeit with some degree of imprecision are avaialble by reference and I'd suspect they're memorized by most radiologists reading mammograms and the breast surgeons involved in tested positives-- even if they may not be able to calculate them. If the doctor doesn't have them memorized-- they should be available by referencing the relevant guideline.

[User23]

I've never once in my life been able to give real informed consent to a physician, because I've never had one able to inform me quantitatively of the risks and benefits of accepting or refusing treatment. So like, I assume, everyone else I pretty much just have to take what the doctor says on blind faith. Since the vast majority of physicians are good people who actually want to help their patients, I'm not entirely uncomfortable with this, but it's still troubling given how many people die every year as a result of interventions or complications thereof.

[rcdmd]

I too wish everything in medicine was cut and dry. But oftentimes precise numbers are unavailable. More qualitative reasoning such as "high risk," "serious morbidity or mortality" is usually given in medical assessments. Plans are developed based off that assessment. Doctors and patients routinely make well-considered decisions and get consent knowing that exact numbers aren't known. On the other hand, many treatments (pharmaceuticals and screening being 2 major ones) are backed by very reliable studies where numbers are known.

[Nomentatus]

Yet the point is that even when the numbers are absolutely clear cut and are more than relevant to medical decision making, doctors' training doesn't help them reason their way out of a wet paper bag. They're hopeless even when they're provided with a problem that has the equivalent of training wheels and handrails.